Electrical cable



Oct. 9,1928. 1,686,782

H. V. WODTKE ELECTRICAL CABLE Filed 00ft. 14, 1922 lnvnhr: Ham V'Wodi Patented Oct. 9, 1928.

UNITED STATES PATENT OFFICE.

HANS V. WODTKE, OF BUFFALO, NEW YORKfASS IGNOR, BY MESNE ASSIGNMENTS, TO GENERAL CABLE CORPORATION, 01 NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

. ELECTRICAL CABLE. I

Application flledflctober 14, 1922. Serial No. 594,440.

The present invention relates generally to insulated electric cables and more partlcularly to that type .of cable which contains one or more flexible conductors. This type of cable, although adapted for more general use, is particularly adapted and more commonly used to supply current to portable electrical devices such as lamps, heating appliances, motor driven household appllances and tools.

The principal object of the invention 1s to improve the construction of such a cable and provide an improved cable which Wlll be exceedingly durable and well adapted to withstand the rough physical treatment to which such cables or cords are often unwittingly subjected as well as the usually disastrous effects of a current in excess of that for which the conductors were designed.

a The invention will be best understood by reference to the following description, when taken in connection with the accompanying drawings of one specific embodiment thereo while itsscope will be more particularly pointed out in'the appended claim.

In the drawings:

Figure 1 is a perspective view of an electric cable exemplifymg the invention, on a somewhat enlarged scale; and I Figure 2 is a cross-sectional view of the same, on a still larger scale.

Referring to the drawings, and to the em bodiment of the invention which is selected for exemplification, there is shown an electric cable comprisin two conductors 4, each composed of a mu tiplicity of strands of wire of cod conductlvity, suchas copper, associated with one another in any suitable manner. Each of theseconductors is provided with a covering 6, such as a thin layer of cotton helically wound thereon. About this covering is an inner jacket 8, of appropriate' vulcanizable material, such as an insulating' rubber compound.

Surrounding each inner rubber jacket is an intermediate jacket 10, comprising a number of strands of material which is preferably non-combustible, such as asbestos. These strands are suitably assembled about the inner jacket as by braiding or winding the same thereon after the latter has been partly cured. As shown in the drawing, the strands of the jacket 10 are helically wound tightly upon the somewhat plastic.

In the valleys presented by adjacent portions of the intermediate..,jackets 10 are 'fillers 12, each comprising a plurality of relatively large cross-section strands which may be of such a character as to impart high tensile strength to the assembly. These fillers present a rounded surface between the assembled conductors over whiclrto form the outer. jacket and promote flexibility by the elimination of the relatively stifl'er rubber is an outer jacket 13 of suitable vulcanizable material, such as appropriate rubber compound which is im ervious to Water and air. Preferably, the ru ber compound is black, contains metallic oxides in addition to the usual ingredients, and is molded under relatively great pressure, all of which increases its heat conductivity. Excellent results have been secured by the use of 65 per cent of zincoxide although it is possible to employ other oxides such as iron and aluminum."

The external-surface of the outer jacket is preferably corrugated, or ribbed and herein is provided with a multiplicity of longitudinal ribs 14:, which possess several advantages, among them the fact that they add to the heat radiating surface, they permit a desirable degree of flexibility by s reading apart on a curve, as represented at the righthand side of Fig. 1; and they readily adapt themselves to openings of various sizes, within reasonable limits, while still afi'ording a proper degree of frictional contact therewith. This is desirable Where the cable jacket 8 when-it is San is inserted in an opening leading to a terminal of a socket or appliance to which the "cable is connected. It is found in practice that the cable can be forced into an opening with which it has a snug fit with greater facility than a cable which has a smooth external surface. -The material of the external jacket '13 may be applied by any one of the well known processes which is best adapted to the purpose. When the material has been appliedthe assembled cable is placed between molds which are brought together to com pact'the cable, forcing the assembled parts into intimate contact, 'filling all voids and excluding all air from the cable. If the molds are correspondingly shaped the outer jacket will be ribbed or grooved as shown. The entire cable is then subjected to vulcanizing heat which cures the outer jacket and completes the curing of the individual I insulation upon the conductors.

The cable when in service, and when subjected to severe tests, is found to have a life many times greater than other cables at present available in the trade for like purposes. Tests have been made by purposely short-circuiting the conductors and raising the amperage of the current. It is found that this cable shows a lower temand the fact that this jacket is combined with an intermediate jacket of non-combustible material. It may be that the highly compressed condition of the inner jackets I a about the conductors is another factor.

The use of the outer jacket of rubber has another important advantage, namely: that it renders the cable entirely water-proof, so that it may be submerged in water without the slightest danger. This is of course important because the outer braided cotton covers usually employed absorb much moisture, and this is found to be destructive to the cables. The rubber covering is also advantageous as compared with a cotton cover, because the latter separates when bent, and the next time is apt to bend at the same place, thus eventually causing weakening and breaking of the conductors, as well as admitting moisture to the interior of the cable.

Having thus described one embodiment of the invention, but without limiting myself thereto, what I claim and desire by Letters *Patent to secure is:

An electrical cable comprising, in com-' bination, a pair of conductors, inner jackets of vulcanizable material, one about each of said conductors, and intermediate jackets of non-combustible, fibrous material, one about each inner jacket" and embedded therein, fibrous, non-combustible, filler material disposed in the valleys presented by adjacent portions of said intermediate j ackets, and an outer molded cylindrical jacket of flexible vulcanizable material of relatively high thermal conductivity, the said 

